New designs of shoes, and particularly shoes for sports or other active wear, have provided improvements in the support, cushioning and stability of the shoe in an effort to reduce injuries to the feet, ankles and knees. One aspect of active wear shoe design which has been overlooked, however, is the configuration and surface characteristics of the insole of the shoe as they relate to the ability of the insole to maintain the foot and sock relatively dry and insulated from the sole of the shoe, and the extent which the foot and sock are permitted to move within the shoe.
Most insoles for active wear shoes are formed of a cushioning material such as rubber, foam or the like whose uppermost surface is covered by a sheet of cloth or leather which contacts the sock of the wearer's foot. One problem with this type of insole is that the rubber or foam absorbs moisture from the sock like a sponge and does not allow the sock to dry. The cloth or leather upper layer of some insoles are provided with tiny spaced perforations to help channel away the moisture from the sock, and to provide ventilation, but the moisture is not prevented from being absorbed by the insole and simply flows back through the perforations to the sock. Additional ventilation openings are provided in the insole and/or fabric sides of the shoe in some designs, but most of the moisture is nevertheless permitted to collect and pool in the insole which prevents the sock from drying.
Another problem with prior art insoles for active wear shoes involves a failure to control the motion of the sock and foot of the wearer along the insole. This affects both the comfort and performance of the shoe. For example, certain activities such as the play of tennis on clay courts and soccer on grass result in substantial movement of the shoe with respect to the playing surface. In these types of activities, it is desirable to limit the movement of the foot and sock with respect to the insole of the shoe for added comfort and to optimize the performance of the shoe. On the other hand, comfort and performance of the shoe dictate that the foot and sock be permitted more movement within shoes intended for use in activities such as basketball, racquetball and aerobics which are typically played on a lacquered hardwood floor wherein limited movement of the shoe relative to the playing surface is permitted.
Prior art insoles can generally be divided into two categories, both of which fail to take into account the movement of the foot and sock within the shoe and the type of surface on which the shoe is utilized. In some prior art designs, the top surface of the insole is formed of a tacky or sticky material having a high coefficient of friction compared to a coefficient of friction of the skin of the foot. Active wear shoes with this type of insole have been found to create blisters on the foot because during use the sock is held in a fixed position against the insole while the foot moves within the sock. The rubbing motion of the foot within the sock creates severe blistering and discomfort, particularly in activities such as basketball and the like played on hardwood floors which permit limited motion of the shoe therealong.
The other general category of insole designs comprises a rubber or foam bottom layer which is covered by an overlayer of cloth or leather having a relatively slippery or slick surface with a much lower coefficient of friction compared to that of the skin of the wearer's foot. Insoles of this type help avoid the blistering problem because the foot and sock move as a unit relative to the slippery top layer of the insole, instead of the foot moving within the sock. The problem with these insoles is that movement of the sock and foot of the wearer is often completely unrestricted and the toes are permitted to violently slide into the front portion of the shoe causing bruising or even fractures of the toes. In addition, undue movement of the foot and sock gives the wearer a feeling of lack of control of the shoe, particularly in activities where the shoe readily slides along the playing surface.